The influence of shape on apparent area: a new demonstration.

It has long been recognised that the apparent area of a form is influenced by its shape, and it has generally been accepted that when a more compact and a more diverse form of the same physical area are compared, the more compact is judged smaller. Experiments are reported which demonstrate that when the apparent area of an isosceles triangle is bisected, the reverse of this principle holds. It is shown that when the apparent areas of a triangle and trapezium are being compared the relative location of the forms being judged determines the direction of the error typically found. Three theories of apparent area are discussed, and reasons for rejecting them put forward. It is concluded that no adequate theory has yet been proposed.